It is the oldest independent, full-distance triathlon competed in the continental United States. It is an unmatched test of human endurance painted against equally unmatched scenery of Sonoma County.

More than 1,000 competitors will toe the starting line early Saturday morning at Johnson's Beach on the Russian River in Guerneville. They'll be poised to take on the challenges that are a triathlon — 2.4 miles of swimming, 112 miles of biking and a run of 26.2 miles.

The first wave of competitors will hit the water at 6:30 a.m. for two loops on the river course. For those best equipped to meet the challenges ahead, the finish line will be about nine hours away. But winning is not the real pursuit. Rather, it's about conquering personal limits, so hours after the winners are cheered across the finish line at Windsor High School, others will still be on the course trying to stretch themselves to reach individual glory.

The competitors' bicycles will be waiting for them when they climb out of the water and the 112 miles they'll face will take them along a course that covers a mix of terrain and travels through the Russian River, Dry Creek, Alexander Valley and Chalk Hill grape-growing regions. Race organizers like to point out that with slightly less than 4,000 feet of climbing for the entire bike course, athletes find the course to be challenging but not overwhelming.

The biking course brings the field to Windsor High School where they dismount and begin a run 26.2 miles — the traditional marathon distance. It comprises three loops from the high school — on a zigzag course through the neighborhoods south of Windsor to a turnaround near the western edge of the Sonoma County Airport.

After three loops on the running course, the lead runners should be approaching the finish line at approximately 3:30 p.m.

Eduardo Sturla of Argentina, a four-time Ironman Triathlon champion who is a pre-race favorite, will be participating in his first Vineman Triathlon. In 2009, Sturla competed in the Ironman 70.3 Vineman Triathlon (formerly known as the Half Vineman Triathlon).

"I loved the race, organization, the place, weather and the people," Sturla said in an email. "Since then I started to consider Santa Rosa as an option for training. In 2011, I came back just for training and that was when I fell in love with Sonoma County."

The Full Vineman Triathlon is not the only endurance event happening Saturday.

A field of 450 women will be competing along the same course in Barb's Race. The half-triathlon was developed as a fundraising event for local cancer-related groups. This will be the 13th edition of Barb's Race, which has raised more than $600,000.

A third event, the Vineman AquaBike, also happens Saturday. It comprises the first two legs of a traditional triathlon — swimming and biking — and is competed at both the full and half distances.